The Giona is a ‘torrent’, or

intermittent stream Intermittent, temporary or seasonal rivers or streams cease to flow every year or at least twice every five years.(Tzoraki et al., 2007) Such rivers drain large arid and semi-arid areas, covering approximately a third of the earth's surface. ...

, which rises on the slopes of Monte Tamaro, in the

Swiss Swiss may refer to: * the adjectival form of Switzerland * Swiss people Places * Swiss, Missouri * Swiss, North Carolina *Swiss, West Virginia * Swiss, Wisconsin Other uses *Swiss-system tournament, in various games and sports *Swiss Internation ...

canton of

Ticino Ticino (), sometimes Tessin (), officially the Republic and Canton of Ticino or less formally the Canton of Ticino,, informally ''Canton Ticino'' ; lmo, Canton Tesin ; german: Kanton Tessin ; french: Canton du Tessin ; rm, Chantun dal Tessin . ...

. After about , it enters the

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

province of Varese The province of Varese ( it, provincia di Varese) is a Provinces of Italy, province in the region of Lombardy in northern Italy. Its capital is the city of Varese (population of 80,857 inhabitants), but its largest city is Busto Arsizio. The head ...

, forming the Val Veddasca before entering

Lake Maggiore Lake Maggiore (, ; it, Lago Maggiore ; lmo, label=Western Lombard, Lagh Maggior; pms, Lagh Magior; literally 'Greater Lake') or Verbano (; la, Lacus Verbanus) is a large lake located on the south side of the Alps. It is the second largest la ...

Maccagno Maccagno was a ''comune'' (municipality) of 2,000 inhabitants located in the province of Varese in the Italian region Lombardy, located in the Val Veddasca about 70 km northwest of Milan and about 25 km northwest of Varese. On 1 January ...

. Its course passes through the communes of

Indemini Indemini () is a former municipality in the district of Locarno in the canton of Ticino in Switzerland. On 25 April 2010, the former municipalities of Caviano, Contone, Gerra Gambarogno, Indemini, Magadino, Piazzogna, San Nazzaro, Sant'A ...

in Switzerland and

Veddasca Veddasca was a ''comune'' (municipality) in the Province of Varese in the Italian region Lombardy, located about northwest of Milan and about north of Varese in the Val Veddasca, on the border with Switzerland. In 2014 it merges with Maccagno ...

Curiglia con Monteviasco Curiglia con Monteviasco is a ''comune'' (municipality) in the Province of Varese in the Italian region Lombardy, located about northwest of Milan and about northwest of Varese Varese ( , , or ; lmo, label= Varesino, Varés ; la, Baretiu ...

Dumenza Dumenza is a ''comune'' (municipality) in the Province of Varese in the Italian region of Lombardy, located about northwest of Milan and about north of Varese, on the border with Switzerland. The municipality of Dumenza contains the ''frazion ...

and

in Italy. The fish found in the river are predominantly

Salmonidae Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefis ...

Cyprinid Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest verte ...

ae and

Cottidae The Cottidae are a family of fish in the superfamily Cottoidea, the sculpins. It is the largest sculpin family, with about 275 species in 70 genera.Kane, E. A. and T. E. Higham. (2012)Life in the flow lane: differences in pectoral fin morphology ...

, in particular

brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

, grayling, chub,

vairone ''Telestes muticellus'' is a species of ray-finned fish in the family Cyprinidae. Commonly known as vairone, it is found in France, Italy, and Switzerland. Its natural habitats are river A river is a natural flowing watercourse, us ...

and

European bullhead The European bullhead (''Cottus gobio'') is a freshwater fish that is widely distributed in Europe, mainly in rivers. It is a member of the family Cottidae, a type of sculpin. It is also known as the miller's thumb, freshwater sculpin, common bu ...

. The river is put to use as a source of

hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, converting the Pot ...

Notes

Rivers of Italy Rivers of Ticino Rivers of Lombardy Rivers of the Province of Varese International rivers of Europe Rivers of Switzerland {{Italy-river-stub